Among the most overlooked video accessories are outdoor windscreens for microphones. Much of a video crew’s work is outdoors and random wind noise is one of the most difficult anomalies to control. This means some sound operators, who work in extreme environments, spend as much money on wind protection gear as the microphones themselves.
Capturing pro audio indoors is much less of a challenge than outdoors. In face, the ability to record good sound outdoors is considered one of the top skills of a professional sound operator. It not only requires specific knowledge of how to manage wind noise, but the right tools to do the job. Those tools, by the way, can get expensive.
One bit of confusion is the difference between windscreens and pop filters. Neumann, the high-end microphone maker, says the main purpose of a windscreen is to protect the mic capsule from windblasts. Windscreens, as expected, are mainly used for outdoor field recording.
However, windscreens also are used as protection against “pops,” the kind of noises that happen inside studios when certain speech sounds such as Ps and Bs hit the microphone membrane at close distance. These speech sounds are also called “plosives,” because they are created by releasing a small blast of air. Pop screens are designed for this problem, Neumann said, though some users wrongly employ windscreens. This is not what a windscreen is designed for.
Rycote Stereo Cyclone DMS (Double Mid-Side)
Whenever working outdoors — no matter the conditions — use a windshield to reduce any chance of wind effecting the mic’s capsule. There is no good way to get rid of unwanted wind noise on the recording. In extreme cases, it is also possible to damage the mic’s capsule due to prolonged exposure to wind.
With outdoor wind, many factors come into play. These can include environment conditions such as the nature of the air flow compared to the type of microphone being used and its characteristics. Since outdoor conditions are unpredictable, professional sound operators are always prepared for all conditions. No one wants to hear the wind is too high to capture intelligible audio.
Shotgun in blimp windscreen
Microphones used outdoors include shotguns, which are very directional and subject to wind noise. They also include lavaliers, which are mostly omni-directional, and handheld mics, which are mostly omni as well. Omni-directional mics are less sensitive than directional to wind noise, but still need wind protection.
There are three basic types of wind protection for microphones, including foam windscreens, windsocks or windjammers and blimps. Each has a role in preventing wind noise from ruining the audio.
Azden, a microphone manufacturer for video crews, describes wind noise as sounding like a bass-heavy, low rumbling, “thumping” or “fwapping” in the video’s audio track. This typically happens in the sub-500Hz range of the frequency spectrum. Since the frequencies of the human voice typically lie between 85 Hz – 265 Hz, dialog can be directly affected by wind noise and can make it completely unintelligible and unusable.
Fur and foam
The sound operator typically uses some type of material around the mic to reduce noise on a outdoor video recording. This acoustic noise reduction is typically measured in dB or decibels. Attenuation can be achieved, Azden wrote, with some sort of porous and/or wispy barrier (foam, plastic mesh, fabric or faux-fur in various combinations) to create a “chamber” of sorts, with the microphone capsule suspended and protected in the middle.
Outdoors, the most effective microphone wind protection must first diffuse the wind and normalize the air pressure near the mic capsule, essentially deadening the air disturbance all around the microphone. With a bare microphone barrel, air can easily flow over the microphone’s outer case, causing disturbance in the immediate vicinity of the microphone capsule.
Adding the protective barrier of a windscreen will diffuse wind around the mic capsule, forcing air to move out and around the foam, while still allowing soundwaves to penetrate the material.
Various wind protection products have different acoustic properties, with differing acoustic transparencies. The acoustic transparency of any windscreen cover will have a greater or lesser effect on the audio, depending on the material.
A less porous material made of a thicker, denser fabric, will show an attenuation of sound at higher frequencies. A more porous and less dense fabric will have a lesser effect on high frequencies (therefore more transparent), but would be more vulnerable to noise created by wind.
Rycote Windshield Kit
There is always a trade-off between the acoustic transparency and the wind-blocking capability of a windscreen cover. The bigger the dead-air “chamber” created around the mic capsule, the better. Basically, the more protective material around the microphone, the more adjustments may have to made to achieve the desired sound.
Simple, foam-type windscreens are fine for indoor use, as air movement indoors is typically less than one meter per second. Foam will provide up to 15-20 dB of noise attenuation, while keeping the mic’s high frequency loss to a minimum.
Usually, these types of foam windscreens are an open-cell foam material like polyurethane.
Windjammers are foam/faux-fur combination windscreens. A synthetic “fur” material is attached to the outer part of a polyurethane foam windscreen to better disperse air movement around the microphone capsule. A longer fur material — typically 1.5-inches or more in length — is desired, as it creates less air friction near the mic capsule, allowing air to move through it. This style will typically provide near 25 dB in wind noise reduction with winds up to six meters per second. Sometimes, a windjammer is designed to slip directly over a microphone’s included foam windscreen.
Blimps are essentially plastic mesh material, with a thin layer of foam inside the mesh. These will have a much larger circumference than the typical foam windscreen or windjammer. They are usually “pill” shaped, but much larger in size.
Blimps provide a larger open-air chamber around the microphone, creating even more space between the moving air and the mic’s capsule. Using a blimp with an additional faux-fur slip-on windshield will add the last level of wind protection, and with these measures in place, one can achieve up to 50 dB of wind noise reduction with wind speeds more than six meters per second.
Rycote Mid-Side Stereo Blimp
However, with the large static air chamber, foam layer and faux-fur material surrounding the mic, there’s a greater potential for loss of high-frequencies in a recording. Boosting the high frequencies in post-production is one way to help counteract this effect.
Video crews should choose the amount of wind protection they need based on where they are located and the type of work they do. Crews that work mostly indoors, need little wind protection. However, crews that work mostly outdoors in extreme conditions need the best protection available.
Nothing can ruin outdoor sound quicker than wind. It can also ruin the reputation of a sound operator just as quickly. So be prepared with the skills and high costs if you record sound in windy conditions.
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